19:Enthalpy Pt.1 Flashcards
What is the symbol for enthalpy change
ΔH
Is ΔH positive or negative in an exothermic reaction
negative
Is ΔH positive or negative in an endothermic reaction
positive
What is the unit for enthalpy change
kJmol¯¹
Will combustion have a positive or negative enthalpy change
negative because it is exothermic
What are standard conditions
Pressure: 1 atmosphere (100 kPa)
Temp: 25℃ (unless stated otherwise)
What is the symbol for standard enthalpy change
ΔHϴ
What is standard enthalpy change
Enthalpy change measured under standard conditions
What is standard state
A substance’s physical state under standard conditions.
eg. water is a liquid in standard state
What is enthalpy change of reaction (ΔrH) of a substance
The enthalpy change when the number moles shown in the equation react to form the products.
What is enthalpy change of combustion (ΔcH) of a substance
The enthalpy change when 1 mol of a substance is burned completely in oxygen
What is enthalpy change of formation ( ΔfH) of a substance
The enthalpy change when 1 mol of a substance is formed from its elements
What is enthalpy change of neutralisation (ΔneutH) of a substance
The enthalpy change when 1 mol of water is formed in a neutralisation
What is the equation for heat evolved or absorbed
q = mCΔT
q: heat (J)
m: mass (usually in g)
C: specific heat capacity (J g¯¹ K¯¹)
ΔT: Temperature change (℃)
What is the specific heat capacity of water
4.18 J g¯¹ K¯¹
